The present invention relates to a plurality of work pieces that are joined together by spot welding. A combination of work pieces according to the preamble of claim 1 is known from JP-U-59 60050.

A vehicle body such as an automotive body typically includes a center pillar located between a front door and a rear door on each side of the vehicle body as an important part of a vehicle body framework. A center pillar typically includes a pair of work pieces located on the outboard side and inboard side of the vehicle body in a mutually opposing relationship and joined to each other by spot welding the side edges thereof so as to define a rectangular closed cross section. To facilitate the spot welding process, at least one of the work pieces is provided with flanges for spot welding along either side edge thereof (see Japanese patent laid open publication No. 06-278466).

When spot welding such a flange of a work piece to the other work piece which may be provided with a corresponding flange, it is necessary to perform spot welding at a plurality of locations arranged along the length of the flange, and the locations of spot welding are required to be specifically determined so that a desired welding strength may be achieved. Conventionally, to guide a welder to perform spot welding at such selected locations with a required accuracy, it was practiced to form dents or recesses that serve as markers for a welder at pre-selected locations during the preceding stamping process.

However, if such dents or recesses are excessively deep and/or extensive, they may reduce the mechanical strength of such parts (see JP-A-7 172344), and are therefore typically so small that a welder may have some difficulty in recognizing them. Also, the spot welding may be performed from the inboard side or outboard side depending on the facilities of the assembly plant and the particular welding procedure, and there may be some difficulty in ensuring the quality of the welding work depending on from which side the welding is performed.

In view of such problems of the prior art, a primary object of the present invention is to provide work pieces provided with marks for determining locations for spot welding which are easy to recognize, and simplifies the task of managing the quality of welding work.

According to the present invention, such a task can be accomplished by providing a combination of work pieces according to claim 1.

Thus, according to the present invention, highly recognizable marks for indicating locations for spot welding can be formed by the wavy shape of the lateral flange of the first work piece. As opposed to dents or recesses which cannot be deep enough to be readily recognizable owing to the limit in the thickness of the work piece, the wavy shape may be of such dimensions as to permit required recognizability without reducing the mechanical strength of the welded parts or the affected work piece. To provide a margin for the positional precision of each location for welding, each peak may include a flattened straight section having a certain length corresponding to a designated area for spot welding.

For avoiding any ill effect from a notch sensitivity that could be caused by the wavy shape of the edge of the lateral flange, each dip may be defined by an arcuate segment having a concave side directed outward, and the straight section of each peak may be smoothly connected to the adjacent dip via an arcuate segment having a convex side directed outward.

If dents or recesses for marking spot welded locations are formed on a side of the second work piece facing away from the first work piece, the locations for spot welding can be recognized not only from the side of the first work piece but also from the side of the second work piece.

The present invention is particularly advantageous, not limitatively, when spot welding the parts of a monocoque vehicle body surrounding door openings.

Now the present invention is described in the following with reference to the appended drawings, in which:

• Figure 1 is an inboard side view of a vehicle body frame top which the present invention can be applied;
• Figure 2 is an enlarged fragmentary perspective view of the part indicated by arrow II in Figure 1;
• Figure 3 is a sectional view taken along line III-III of Figure 2 to show how an opening trim can be fitted on the edge of the welded panel assembly; and
• Figure 4 is an enlarged fragmentary view of a part of Figure 2.

Referring to Figure 1, the illustrated vehicle body frame 1 comprises a side sill 2 extending in a lower part of each side part thereof in a fore-and-aft direction. The illustrated vehicle body frame 1 is that of a four-door passenger car, and includes a center pillar 3 located between a pair of openings for a front door and a rear door.

As shown in Figure 2, the center pillar 3 comprises a pair of work pieces or a center pillar outer 5 forming a part of an outer side panel 4 and a center pillar inner 6 placed onto the center pillar outer 5 from the inboard side thereof. As shown in Figure 3, a center pillar stiffener 7 is interposed between the center pillar outer 5 and center pillar inner 6.

In the illustrated embodiment, the spot welding for the inner and outer frame members surrounding the door openings including the parts for the center pillar is performed along a part of the edge of the front door opening indicated by L1 in Figure 1 and along a part of the edge of the rear door opening indicated by L2 in Figure 1.

The center pillar inner 6 is generally spaced away from the stiffener 7, but is provided with a flange 8 which is bent to the outboard side with respect to the remaining part of the center pillar inner 6 along the edges indicated by L1 and L2 in Figure 1. The flange 8 is closely placed onto the stiffener 7 which is in turn closely placed onto the center pillar outer 5.

The flange 8 is provided with an outer edge given with a wavy profile as best illustrated in Figure 2 while the outer edge of the center pillar outer 5 is substantially linear or slightly curved as required by the designed outer profile of the finished center pillar. The outer edge of each peak of the wavy edge profile of the flange 8 substantially coincides with the outer edge of the center pillar outer 5. Each dip of the wavy edge profile of the flange 8 is set back by a distance from the peaks 8a of the wavy edge profile of the flange 8 as illustrated in Figure 3. In the illustrated embodiment, the edge of the stiffener 7 is substantially conformal with the wave edge of the flange 8 of the center pillar inner 6. However, the edge of the stiffener 7 may be substantially linear or slightly curved as required, and coincide with the outer edge of each peak of the wavy edge profile of the flange 8 or the outer edge of each dip of the wavy edge profile of the flange 8.

The edge of this assembly is fitted with an opening trim 9 (Figure 3) in a work process following the spot welding process, and the opening trim 9 includes a slot 9b defined by a pair of mutually opposing walls for receiving the edge of this assembly and a pair of mutually opposing clamping lips 9a formed on the mutually opposing walls. The distance C between the edge of this assembly (which may be an outer edge of the peaks 8a of the flange 8 of the center pillar inner 6 or the outer edge of the center pillar outer 5) and the dips 8b is selected such that a clamping lip 9a of the opening trim 9 is resiliently pushed against the surface of the center pillar inner 6 when the opening trim 9 is attached. In other words, the clamping lips 9a are spaced from a bottom of the slot by a distance D greater than the distance C between the edge of the assembly and the dips 8b of the lateral flange 8 (D>C). In Figure 2, the peaks 8a of the lateral flange 8 are offset from the edge of the center pillar outer 5 in a somewhat exaggerated manner, and this offset may be extremely small in reality. These two edges may substantially coincide with each other. Therefore, the distance C substantially corresponds to the depth of the dips 8b. If the distance C is excessive, the clamping lips 9a may fall into a dip 8b when the opening trim 9 is attached to the edge of the flange 8. If it is the case, the opposing clamping lips 9a designed to clamp the center pillar outer 5 and center pillar inner 6 from both sides may not provide an adequate clamping force to hold the opening trim 9 in place. By selecting the distance C at an appropriate level as discussed above, the clamping lips 9a are prevented from falling into a dip 8b when the opening trim 9 is attached to the flange 8, and the mutually opposing clamping lips 9a are enabled to clamp the center pillar outer 5 and center pillar inner 6 without fail so that the opening trim 9 is prevented from being dislodged from the flange 8.

The flange 8 of the center pillar inner 6 is thus given with a wavy formed edge as discussed above, and the peaks 8a provide a guide for selecting the locations 11 for performing the spot welding as illustrated in Figure 2. As opposed to the small dents used in the conventional arrangement, the welder is enabled to identify the locations for spot welding both clearly and precisely. The flange 8 is provided for the convenience of spot welding, and is therefore not required to have a uniform width in parts where spot welding is not performed to ensure a required mechanical strength as long as the parts to which the opening trims 9a are attached are given with a necessary thickness. The wavy form of the edge of the flange 8 satisfies such requirements, and the removal of the material of the center pillar inner 6 to form the dips 8b of the wavy form contributes to the reduction in the weight of the center pillar inner 6.

A specific example of the wavy form is given in Figure 4. Each location for spot welding (which is selected according to a particular spot welding plan) is selected at a midpoint between two adjacent peaks 8a, but is designated as an area 12 for spot welding by considering a tolerance S for a positional error along the length of the flange 8. In the example illustrated in Figure 4, for each given location 11 for spot welding, a track-shaped area defined by a pair of mutually circumscribing circles (having a radius of Rs) arranged along the length of the flange 8 and centered around the spot welding location defines an area 12 for spot welding.

Each peak 8a of the wavy shaped edge may be flattened and extend by a length corresponding to the length of the straight section of the track shape as illustrated in Figure 2. Each dip 8b may be formed by an arcuate segment (having a curvature radius of R) having a desired depth as measured from the straight sections. The transitional segment extending between each straight section and the adjacent dip 8b may be defined by a circle having a radius of Rc concentric to the corresponding one of the aforementioned circles having the radius Rs, Rc being given as a sum of the radius Rs and a desired margin of tolerance. For instance, the radius of each basic circle Rs may be 5 mm, and the radius Rc for an added margin may be 6 (5+1) mm. In other words, each dip 8b includes an arcuate segment having a concave side directed outward, and the straight section of each peak is smoothly connected to the adjacent dip via an arcuate segment having a convex side directed outward.

By thus forming the peaks 8a and dips 8b of the wavy shape of the edge of the flange 8 with moderate arcuate segments (having the radii of curvature of Rs and Rc) in addition to the straight sections, the edge is given with a smooth profile so that cracks owing to stress concentration are prevented from developing at the time of a vehicle crash. The locations for spot welding can be readily determined from the locations of the peaks 8a and the welding work can be performed by visually noting the locations of the peaks 8a so that the welding work can be simplified. Also, because each peak 8a is defined so as to correspond to a spot welding area having a certain expanse and provide a certain positional tolerance, it can be readily determined that each spot welded locations is selected to design, and the quality control of the spot welding part can be simplified.

Because the wave shaped edge is formed in such manner that the edge of the flange includes peaks 8a and dips 8b in an alternating manner as seen in the plane of the flange, it can be easily formed by trimming the corresponding edge of the center pillar inner 6 in a corresponding manner during the stamping process. Therefore, providing markings for spot welding work does not involve additional manufacturing step or an increase in the amount of work.

In the illustrated embodiment, as shown in Figure 3, a plurality of dents 13 are provided on the outboard side of the center pillar outer 5. Depending on the facility of the assembly plant and/or the procedure of the welding work, the welding may have to be performed from both the outboard and inboard sides. The wave shape of the edge of the flange of the center pillar inner may be used as a marking when welding from the inboard side, and the dent 13 may be used as a marking when welding from the outboard side.

Typically, the interior of a vehicle body is dimmer than the outside because the lighting is more readily available for work outside of the vehicle body. Therefore, the dents 13 may be adequate as a marking for the spot welding work performed from outside the vehicle body. The wavy shaped edge provides a more readily discernible marking for the spot welding work which is often required to be performed under a dimmer condition.

The foregoing embodiment was directed to a center pillar 3, but the present invention is by no means limited to a center pillar but may also be applied to any work pieces that are spot welded as long as at least one of the work pieces is provided with a flange and the two work pieces are spot welded to each other via the flange.

Although the present invention has been described in terms of preferred embodiments thereof, it is obvious to a person skilled in the art that various alterations and modifications are possible without departing from the scope of the present invention which is set forth in the appended claims.